In a printer having a duplexer, each sheet of media has to be repositioned relative to a desired location in the media return path of the duplexer prior to the sheet of media being returned into the media input path of the printer. Repositioning of the sheet of media is required due to the sheet of media possibly being misaligned during its initial advancement through the printer when printing occurs on a first side of the sheet of media.
This misalignment may be to the left or right of the desired location of the sheet of media. The sheet of media also may be angled relative to its desired location. To have accurate positioning of each sheet of media during its return to the printing area of the printer so that printing on a second side of the sheet of media is accurate, the sheet of media must be accurately repositioned relative to a known location.
One previously suggested arrangement for repositioning each sheet of media in a duplexer has been to move a side surface of the sheet of media away from a reference edge, which provides the desired alignment location of the sheet of media, and then return the side surface of the sheet of media into alignment with the reference edge during its return to the printing area of the printer. This would insure that the sheet of media, which would interfere with the reference edge due to its misalignment, is positioned away from the reference edge when the leading edge of the sheet of media enters the entrance to the reference edge.
One prior arrangement for moving the sheet of media away from the reference edge has utilized a cam shifting mechanism to move the sheet of media in one direction away from the reference edge so that the reference edge alignment mechanism can align the sheet of media with the reference edge by movement of the sheet of media in the opposite direction until the sheet of media is aligned to the desired location relative to the reference edge. However, this cam shifting mechanism is relatively expensive. It also has some reliability problems due to design complexity.
In a printer having a media path with both simplex and duplex capabilities, a single sheet of media is separated from the top of a stack of sheets of media in a media tray. The sheet of media is then transported through a printer during its printing process.
In a duplex operation, the direction of motion of the sheet of media is reversed after its trailing edge is released from fuser exit rollers of a laser printer, for example. After the direction of motion of the sheet of media is reversed, it must be realigned in the duplexer path to the correct position and orientation prior to entering again into the printer input path. To align the sheet of media with the reference edge to its correct position and orientation, alignment rollers have previously been employed. These alignment rollers are skewed so that they apply both a force perpendicular to the reference edge and a force parallel to the reference edge to advance the sheet of media.
However, when the leading edge of a sheet of media enters the entrance to the reference edge, it could engage the entry end of the reference edge and create a paper jam. This is because the position and orientation of the sheet of media is not known when the leading edge of the sheet of media enters the entrance to the reference edge in its duplex operation. Accordingly, it is necessary to insure that the sheet of media does not engage the entry end of the reference edge when the sheet of media is to be printed on its second side.
One possible arrangement would be to form an angled entry portion reference edge so that the entry portion is not in a position to be engaged by any sheet of media that enters it. However, this creates the problem of the angled reference edge disposing the sheet of media so that it is not returned to the printer in the correct orientation.
If the reference edge were designed with two contiguous segments with the first segment angled to allow for entry of each sheet of media into the entrance of the reference edge and a second reference edge segment oriented for proper presentation of the sheet of media for its return to the printer for printing on its second side, this would appear to solve the problem. However, this arrangement results in a side surface of the sheet of media being forced simultaneously against two media engaging surfaces of the reference edge at an angle to each other. This would cause the sheet of media to be stressed, and the sheet of media may be damaged during alignment.
The media alignment mechanism of the present invention satisfactorily solves the foregoing problem through forming the reference edge of two segments separated from each other by a non-linear portion. The non-linear portion preferably has an S shape in the predetermined media feed path during its return to the printer although any suitable non-linear shape may be employed. The non-linear portion of the media path allows each sheet of media to be aligned simultaneously with each of the two spaced reference edge segments without inducing significant stress in each sheet of media. This avoids any damage to the sheet of media.
When the sheet of media is in the non-linear portion of the media path, the beam of the sheet of media is broken. This allows a side surface of the sheet of media to become aligned with the media engaging surface of the second reference edge segment with which the sheet of media is aligned to return to the printing area of the printer in the desired alignment while the side surface of the sheet of media is still engaging the media engaging surface of the first reference edge segment.
The media alignment mechanism enables entry of each sheet of media into the entrance of the first reference edge segment even when the sheet of media would be in interference with the desired position as defined by the second reference edge segment. The media engaging surface of the first reference edge segment is angled away from the advancing sheet of media to prevent interference between the sheet of media and the entry end of the first reference edge segment. The non-linear portion of the media path of the sheet of media turns the sheet of media between the two reference edge segments to allow the sheet of media to be aligned simultaneously with the media engaging surface of each of the two reference edge segments.
This arrangement breaks the beam of the sheet of media. This arrangement enables the sheet of media to move from alignment with the media engaging surface of the first reference edge segment into alignment with the media engaging surface of the second reference segment.
Each of the two reference edge segments has a separate advancing means for advancing each sheet of media. Each of these advancing means provides both a force substantially perpendicular to the media engaging surface of the reference edge segment and a force parallel to the media engaging surface of the reference edge segment in the same manner as previously used.
During the movement of the sheet of media along the media engaging surface of the first reference edge segment, its leading edge is free to move laterally. This allows alignment of the sheet of media with the media engaging surface of the second reference edge segment by its advancing means when the sheet of media is constrained by the media engaging surface of the first reference edge segment.
As the sheet of media is advanced, one of its side surfaces engages the media engaging surface of the second reference edge segment with this engaging side surface of the sheet of media being shortened in the non-linear portion of the media path while the opposite side surface is lengthened therein. This results from the breaking of the beam of the sheet of media.